NGC2516CXO - NGC 2516 Chandra X-Ray Point Source Catalog

The NGC 2516 Chandra X-Ray Point Source Catalog is the result of
a comprehensive study of the Chandra X-ray observations of the young open
star cluster NGC 2516. The authors have analyzed eight individual
Chandra observations, comprising 5 ACIS and 3 HRC-I observations.
They have combined these datasets to achieve the greatest sensitivity,
reaching down to a threshold level of log f_X = -14.56 (erg/s/cm^2),
or log L_X = 28.69 (erg/s) at the 387 pc distance of NGC 2516. Out of 284
X-ray sources detected, 155 are identified with photometric cluster members,
with very little ambiguity, another 60 with non-members. There are 4 X-ray
sources with two possible optical identifications (one cluster member and
one nonmember for each), with no obvious choice between the two candidates.
These 4 X-ray sources are listed in this Browse table twice, one for each
optical counterpart, hence there are (284 + 4 =) 288 entries. There remain
73 X-ray sources without an optical identification with the authors' optical
catalog stars.

Source_Number
A running sequential identification number in order of
increasing J2000 Right Ascension. This was used by the HEASARC to construct
a name for the X-ray source, using the prefix '[DFM2003] ' recommended by
the Dictionary of Nomenclature of Celestial Objects.

Name
The name of the X-ray source constructed using the prefix '[DFM2003] '
recommended by the Dictionary of Nomenclature of Celestial Objects and
the running sequential identification number (source_number).

RA
The Right Ascension of the X-ray source in the selected equinox. This
was given in J2000 coordinates to a precision of 0.01 seconds of time in the
originating table. It is a weighted average of the individual positions for
sources detected more than once, using the inverse square of the error as the
weight. The quoted value includes a systematic correction of 0.07" based on
matching the X-ray and Jeffries et al. (2001A&A...375..863J)
optical positions.

Dec
The Declination of the X-ray source in the selected equinox. This
was given in J2000 coordinates to a precision of 0.1 arcseconds in the
originating table. It is a weighted average of the individual positions for
sources detected more than once, using the inverse square of the error as the
weight. The quoted value includes a systematic correction of 0.19" based on
matching the X-ray and Jeffries et al. (2001A&A...375..863J) optical
positions.

Photon_Flux
The mean photon flux (or count rate per effective area)
of the X-ray source, in counts/s/cm^2. It is a weighted average of the
individual fluxes for sources detected more than once, using the inverse
square of the error as the weight. More complete details of how the mean
fluxes were calculated are given in Section 3.3 of the published paper.

Number_Detections
The number of Chandra observations in which the
X-ray source was detected.

Jth_Number
The Jeffries et al. (2001A&A...375..863J) or JTH Number, NNNNN,
of the optical counterpart to the X-ray source. JTH stars are denominated
as `Cl* NGC 2516 JTH NNNNN' in the Simbad database. More complete details of
how the X-ray sources and stars were matched are given in Section 4 of the
published paper.

Offset
The offset between the X-ray source and the optical counterpart,
in arcseconds.

Vmag
The V Band magnitude of the optical counterpart to the X-ray source,
from the optical catalog of Jeffries et al. (2001A&A...375..863J), complete to
about V = 20, supplemented by a list of brighter stars, as reoprted by
Jeffries et al. (1997MNRAS.287..350J).

BV_Color
The (B-V) color of the optical counterpart to the X-ray source,
from the optical catalog of Jeffries et al. (2001A&A...375..863J), complete to
about V = 20, supplemented by a list of brighter stars, as reoprted by
Jeffries et al. (1997MNRAS.287..350J).

VI_Color
The (V-I) color of the optical counterpart to the X-ray source,
from the optical catalog of Jeffries et al. (2001A&A...375..863J), complete to
about V = 20, supplemented by a list of brighter stars, as reoprted by
Jeffries et al. (1997MNRAS.287..350J).

Cluster_Flag
This parameter flags whether ('Y') or not ('N') the optical
counterpart to the X-ray source is a member of the NGC 2516 cluster.

Binary_Flag
This parameter flags whether ('Y') or not ('N') the optical
counterpart to the X-ray source is a known binary system.

Log_Lx
The log of the X-ray luminosity of the X-ray source in the 0.1
- 4 keV band, provided that it is a cluster member, in erg/s. (X-ray
luminosities are not provided for the 60 X-ray sources associated with
nonmembers). A distance of 387 pc and an absorption column density of 8.2 x
10^20 cm^-2 (Jeffries et al. 2001A&A...375..863J), corresponding to the
cluster extinction A_V = 0.372, has been assumed for NGC 2516. The methodology
used to convert the count rates into X-ray fluxes is discussed in detail in
Section 3.4 of the published paper.